Hydraulic fracturing fluids containing proppants are used extensively to enhance productivity from hydrocarbon reservoir formations, including carbonate and sandstone formations. During hydraulic fracturing operations, a fracturing treatment fluid is pumped under a pressure and rate sufficient for cracking the formation of the reservoir and creating a fracture. Fracturing operations usually consist of three main stages including a pad fluid stage, a proppant fluid stage, and an overflush fluid stage. The pad fluid stage typically consists of pumping a pad fluid into the formation. The pad fluid is a viscous gelled fluid which initiates and propagates the fractures. Auxiliary fractures can propagate from the fractures to create fracture networks. A fracture network can comprise fractures and auxiliary fractures. Auxiliary fractures can connect the fractures.
The proppant fluid stage involves pumping a proppant fluid into the fractures of the formation. The proppant fluid contains proppants mixed with a viscous gelled fluid or a visco-elastic surfactant fluid. The proppants in the proppant fluid are lodged in the fractures and create conductive fractures through which hydrocarbons flow. The final stage, the overflush stage, includes pumping a viscous, gelled fluid into the fractures to ensure the proppant fluid is pushed inside the fractures. While the three stages have different aims, all three make use of highly viscous and/or gelled fluids to achieve those aims.
A downside of the traditional method is that a high volume of gelled or polymeric materials can be left behind in the fractures. The gelled materials can be concentrated around the proppant in the fractures or can be freely in the fractures. The gelled material acts to block the fractures reducing the fracture conductivity. The hydrocarbons which flow from the reservoir formation are unable to move the gelled materials. Traditional methods for cleaning the fractures involve viscosity breakers or other elements to breakdown the fluid. These traditional methods suffer from an inability to completely cleanup the fractures, leaving residual viscous material and reduced conductivity.